The present invention relates to portable furnaces and more particularly to compact furnaces or warmers to be carried on the person for circulating heat in wearing apparel such as gloves or boots.
Boot warmers wherein a hot liquid is circulated within a boot have been known in the past, for example, as illustrated in U.S. Pat. No. 518,579 issued to Annenberg et al and in U.S. Pat. No. 1,199,914 issued to Mossor. However, such boot warmers provide no compact means for heating the fluid and further require a rather awkward operation in getting the heated fluid into the boot cavities.
U.S. Pat. No. 912,527 issued to Batter on Feb. 16, 1909 discloses a portable boot and body warmer wherein a heater unit of relatively large size is attached to the individual's belt and fluid conduit tubes pass from the individual's belt down his legs and into his shoes or boots. Hand manipulated pumps are provided at the knee level to pump or circulate the fluid throughout the conduits. However, such an apparatus is extremely cumbersome and it is also relatively impractical in this day and age, and it is rather obvious that hunters and outdoor workers would not tolerate such a large amount of paraphernalia and tubes running down the legs and about the waist.
Liquid heater units for body warming purposes which are much more compact than that illustrated in Batter U.S. Pat. No. 912,527 have been developed as may be seen in U.S. Pat. No. 3,737,620. However, this compact heater unit, while being light weight and apparently very effective, is relatively complex and requires the use of nuclear fusion. The expense of such a device would clearly be beyond the reach of the average hunter or outdoor worker. In addition, this reference and the aforementioned reference do not teach how any of the devices disclosed could be more conveniently and economically and compactly utilized as a boot or glove warmer.
A major disadvantage of the economical heating units of the prior art which are utilized to circulate a heated liquid through wearing apparel is that these heating units must be used substantially in an upright position and will not effectively operate at any or all attitudes. In addition, the liquid furnaces of the prior art are, by necessity, too large in size and are cumbersome.
We have discovered that our boot warmer as disclosed in U.S. Pat. No. 4,180,922 is extremely effective. However, there are certain conditions under which this boot warmer cannot be utilized when solid fuel agglomerates are used in the furnace. For example, under some working conditions, as where explosive gases or dusts might be present, an open flame cannot be utilized. Also, in many working conditions, such as in the military and in many other outdoor occupations, there are times when an entire boot or glove or other wearing apparel may become completely submerged in water which would extinguish an ignited solid fuel agglomerate.
A principal object of the present invention is to eliminate these aforementioned disadvantages of the prior art and to provide a compact heating system for wearing apparel which is much more convenient and less expensive than the devices of the prior art.